You are here:
COMPARISON OF SELECTED LOWER EXPLOSIVE LIMIT METERS USED BY USAF AND COMMERCIAL JET FUEL TANK ENTRY PERSONNEL
Jensen, P. A., S. Martin, M. J. Sapko, K. L. Cashdollar, K. E. Mura, L. Smith, D. Fritts, B. A. Blazicko, J. M. Reichert, AND J D. Pleil. COMPARISON OF SELECTED LOWER EXPLOSIVE LIMIT METERS USED BY USAF AND COMMERCIAL JET FUEL TANK ENTRY PERSONNEL. Presented at American Industrial Hygiene Conference and Exposition, Orlando, FL, May 19-25, 2000.
The objective of this task is to develop state-of-the-art methods for measuring xenobiotic compounds, to include the isolation of the analyte from the appropriate matrix (extraction), preconcentration (typically sorbent-based), and analysis via GC/MS and/or LC/MS. Once established, these methods will be applied in small scale pilot studies or demonstration projects. Particular emphasis will be placed on methods which are readily transferable to other laboratories, including those within the Human Exposure and Atmospheric Sciences Division (HEASD), the National Exposure Research Laboratory (NERL), other EPA Laboratories, Program Offices, Regions, and academic institutions.
Specific objectives of this task include the following:
1) Development of GC/MS and LC/MS methods for the measurement of key xenobiotic compounds and their metabolites (to include the pyrethroid pesticides, perfluorinated organic compounds, and the BFRs) in relevant environmental and biological matrices.
2) Development of efficient low cost methods for the extraction and clean up of these compounds collected from relevant matrices.
3) Determination of xenobiotic compound and metabolite concentrations in samples derived from laboratory and field monitoring studies to help assess exposures and evaluate associated risks.
Thousands of military personnel and tens of thousands of civilian workers perform tank entry procedures. OSHA regulations (1910.146) require the internal atmosphere be tested, with a calibrated direct-reading instrument, for oxygen content, flammable gases and vapors, and potential toxic air contaminants before an employee enters the space. The USAF and NIOSH had previously identified the highest worker exposures during removal of fire suppressant foam from the fuel tanks of Hercules C-130 aircraft. In addition, the study noted that jet fuel vapor composition changed with time and ventilation.
In this study, lower explosive limit (LEL) meters were challenged with jet fuel vapor from fuel tanks of a Hercules C-130H and several commercially-available LEL span gases. The meters evaluated were based on three detection technologies: (1) infrared; (2) photoionization; (3) catalytic bead.
All meters were calibrated in accordance with manufacturer's specifications and with manufacturer-supplied calibration gas. All meters were used as provided by the manufacturers except 0.25-inch (ID) Teflon-lined tygon tubing was used in lieu of manufacturersupplied tubing. A Foxboro TVA 1000B, with flame-ionization detector, was used to measure total hydrocarbon content of the jet fuel vapor.
Overall, the FID was most sensitive, the photoionization detectors and infrared detector were second. The catalytic beads appeared bifurcated - Some were responsive and some were not to vapor compositions after ventilation. The traditional catalytic bead technology does not allow for the detection of n-alkanes (>C9); thus, after ventilation of the more-volatile fraction of jet fuel, a potentially-explosive or unsafe environment might go undetected. Overall, some LEL meters may significantly underestimate the explosive potential of jet fuel vapors in tanks after the light-end of jet fuel has been removed. A second major finding of this study is that manufacturer-recommended calibration techniques do not appear to match instrument performance to jet fuel vapor.